Council will be informed

Delay at the geothermal drilling site in Graben-Neudorf: "Safety before speed"

Deutsche Erdwärme explains the delays at the geothermal drilling site in Graben-Neudorf and names an important date in June.

The drilling rig on the drilling site: Another pipe is loaded and fed into the depths. The pipes get thinner and thinner as you go down. If they still have a diameter of 85 centimeters at the top, it is only 16 centimeters at the bottom. Photo: Monika Eisele

by Monica Eisele

May 23, 2023 | 7:35 p.m 2 minutes

Deutsche Erdwärme has planned a so-called well test at the geothermal drilling site in Graben-Neudorf for June . Then, at last, the exact temperature and flow rate could be determined, reported Roman Link, communications and municipal affairs officer, to the Graben-Neudorf municipal council.

With the first borehole one arrived in the area of the Buntsandstein, where the columns with the hot thermal water are. Before that, an independent expert from the University of Potsdam will check the borehole and then release it for the test.

Commissioning of the power plant by early 2025

According to Link, the Q-con company checks the data obtained using a risk study and reports to the mining authority. If the well test is successful, the second well can begin in July. The commissioning of the power plant or heating network can be expected at the end of 2024 or beginning of 2025, Link promised.

The building permit for the geothermal system has been in place since December. "We should be able to move faster on the second well because we can build on the experience from the first well," Link said.

Safety and quality are more important to us than speed.

Roman Link, German Geothermal Energy

Instead of the original three to six months, it now took a year for the German geothermal energy to reach the desired depth. That triggers uncertainties in him and in the population, said municipal councilor Jörg Hartmann (CDU). "There's nothing alarming about that," Link assured.

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“Actually, we are making eight meters an hour. Depending on the subsoil, on some days it's only two meters per hour". Replacing worn drill bits alone takes four to five days and requires additional measurements and quality controls.

The system should be operated for at least 30 years

"Then a drill head jammed and got stuck," reported Link. First, according to the specifications, an attempt had to be made to recover the drill head. This failed. So the area around the drill head was cemented and a new shaft, a so-called sidetrack, was drilled slightly offset.

This required the construction of a ski jump that guides the drill head past the original shaft. All of this requires planning, which in turn is coordinated with the mining authority, said Link.

The insufficient cementing at a depth of between 3,000 and 3,300 meters caused further delays, Link continued. Measurements had shown that the cementing in the upper area of the last section was insufficiently filled. A second attempt at cementing was not technically possible, which is why the decision was made to drill a sidetrack again.

The whole procedure from the draft of the plans to the coordination with the mining authority was repeated. "You can't just look into that depth and see where the problem is or how it can be fixed," explained Link.

The costs of the delay are the company's economic risk, Link replied to a question from municipal councilor Armin **ler (Bündnis 90/Die Grünen). “We want to operate the system for at least 30 years. This is one of the reasons why safety and quality are more important to us than speed,” says Link.

On-site information center expects the 1500th visitor

It is gratifying that there have been no seismic events triggered by the drilling during the entire period. For clarification, Link presented recordings of the measuring stations.

Municipal councilor Thomas Laubner (SPD) wanted to know which substances – possibly dangerous – had been encountered during the drilling. "Unfortunately, we didn't find any gold, but nothing else of concern either," said Link.

If you have any questions or are unclear, you can contact the company at any time. He also referred to the information center at the site, which is in lively use and is expecting its 1,500th visitor these days.